title: An improved bioassay facilitates the screening of repellents against cat flea, Ctenocephalides felis (Siphonaptera: Pulicidae).
abstract: BACKGROUND
  Repellents are a common method for preventing flea bites, making an effective system for flea repellent screening advantageous. We describe an improved technique to facilitate repellent activity screening of numerous plant-based Ctenocephalides felis (cat flea) repellents.
  
  
  RESULTS
  Two long strips of filter paper were impregnated with test compounds (dissolved in ethanol) and ethanol only, respectively. After drying, the two filter papers were glued together along the long side and inserted into a glass tube containing non-fed cat fleas. The distribution of cat fleas in each half of the filter paper was recorded after 30 min to calculate repellency. Results showed that the essential oil of Cinnamomum osmophloeum (from leaf), Taiwania cryptomerioides (from heartwood) and Plectranthus amboinicus (from leaf) exhibits repellent activity against cat fleas in a dose dependent manner. Moreover, the repellent activities against cat fleas of 2% trans-cinnamaldehyde (the main constituent of Ci. osmophloeum essential oil) and 0.5% thymol (the main constituent of P. amboinicus essential oil) are 97.6% and 90.6%, and can persist for up to 4 and 8 h, respectively. These results are comparable to those of 15% DEET.
  
  
  CONCLUSIONS
  The proposed screening technique can facilitate the pre-screening of numerous flea repellents for further evaluation on animal or human subjects.
authors.affiliation: Department of Entomology, National Taiwan University, Taipei, 10617, Taiwan.
authors.forename: Li-Chong
authors.initials: LC
authors.lastname: Su
authors.forename: Chin-Gi
authors.initials: CG
authors.lastname: Huang
authors.forename: Shang-Tzen
authors.initials: ST
authors.lastname: Chang
authors.forename: Shu-Hui
authors.initials: SH
authors.lastname: Yang
authors.forename: Shan-Hui
authors.initials: SH
authors.lastname: Hsu
authors.forename: Wen-Jer
authors.initials: WJ
authors.lastname: Wu
authors.forename: Rong-Nan
authors.initials: RN
authors.lastname: Huang
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000191:economics / Q000379:methods*; D003362:Cost-Benefit Analysis; D004353:Drug Evaluation, Preclinical / Q000191:economics / Q000379:methods*; D007302:Insect Repellents / Q000494:pharmacology*; D010936:Plant Extracts / Q000494:pharmacology*; D005423:Siphonaptera / Q000187:drug effects*
chemical_list: D007302:Insect Repellents; D010936:Plant Extracts
keywords: Cinnamomum osmophloeum; Ctenocephalides felis; essential oil; repellent; thymol; trans-cinnamaldehyde